Production of foam article



April 7, 1970 HANS-DIETRICH KRUG ET PRODUCTION OF FOAM ARTICLE Filed May17, 1966 FIG. I.

FIG. 2.

FIG. 4.

FIG. 5.

INVENTORS HANS-DIETRICH KRUG PETER RUTSCH ATTORNEYS.

United States Patent 3,505,436 PRODUCTION OF FOAM ARTICLE Hans-DietrichKrug, Heidelberg, and Peter Rutsch, Unter Abtsteinach, Germany,assignors to Carl Freudenberg, Weinheim, an der Bergstrasse, Germany, acorporation of Germany Filed May 17, 1966, Ser. No. 550,720 Claimspriority, application Germany, July 1, 1965, F 46,487 Int. Cl. B29d 9/00US. Cl. 264-45 3 Claims ABSTRACT OF THE DISCLOSURE Process of producinga composite foam containing article by positioning in a mold of suitableshape which mold has freely accessible shoulders on both sides thereof,a film draped between and laying on said shoulders, a non-woven fabricand a foamable polyurethane mass, and permitting the polyurethane tobecome foam-form, whereby embedding such foam through said non-wavenfabric and on to said film, adhering said foam to said film without thenecessity of extraneous adhesives, and filling out the mold cavity withthe foam whereby to extend the film to mate with the peripheral portionsof the mold cavity.

This invention relates to the production of foamed articles. It moreparticularly refers to the production of reinforced foam articles.

In the production of shoes, it has often been found desirable to utilizean inner sole and an outer sole. The outer sole material is especiallychosen for its wear characteristics as well as for its customer appealin the esthetic sense. The inner sole is also required to beesthetically pleasing to the customer. In addition, the inner sole alsoserves a utilitarian purpose in that it provides support and cushioningwhereby the comfort of the shoe wearer is increased.

It is often the case that inner soles are made of cork, plastic foam orother resilient material in which case it has been found desirable tocoat that surface of the inner sole adjacent the wearers foot with aflexible, relatively impervious material. The inner sole is usuallyproduced by pasting or gluing the resilient layer to the imperviouscoating therefor.

It is apparent that it is time consuming and cumbersome to produce thecushioning material as a separate part and the impervious coating as aseparate part and then glue the two together. Further this type ofoperation does not lend itself to economical operation in that thecoating film must be exactly fit to the shape of the resilient member.If the film is pulled too tightly over the edge of the resilient member,it tends to stretch in elastically and in some cases even tear. If thefilm is glued too loosely to the resilient member, it buckles and formscreases which impair its appearance as well as impart uncomfortablespots to the final product. In addition, these creases are places oflittle or no adhesion between the resilient member and its coating filmand therefore represent points at which delamination and tearing caninitiate.

It has been proposed to remedy this situation by placing the resilientcoating film in a bipartite mold and to create a foam of the properphysical characteristics and shape on top of this film in the moldcavity. It has been proposed to accomplish this by providing a firstlayer of film in a suitably shaped mold, disposing a foamable materialon this first film in the mold and providing a second film on top of thefoamable material. The ends of the two films are juxtaposed between thetwo half molds such that when the bipartite mold is closed, the ends ofthe two resilient films are pressed together by the meeting faces orflanges of the mold halfs.

After the mold is closed the foamable paste is allowed to foam wherebypressure is exerted upon the resilient films causing them to assume theshape of the mold cavity. The foaming process inherently causes theresilient films and the contained foam to adhere to each other by meansof the heat of foaming as well as the tacky nature of the foam duringits creating. During the foaming process the film and the foam actuallypartially merge together partially dissolving each other or fusingtogether and thus belcoming intermingled whereby excellent adhesion resuts.

As can be appreciated from the above description, it has generally beenbelieved that it was necessary to completely envelop the foam in a pouchof resilient film. Therefore there were always used the two films joinedat their edges in the manner described. This joining of the edges of thetwo films not only creates a pouch for the foam to be created in butalso holds each film tightly whereby creasing of the films due toslackness is substantially eliminated as is the possible tendency of thecoating film to slip with relation to the foam and thus obtain onlypartial coverage thereof.

This described improvement is not the complete answer to problemsexisting in this art since the films tend to be stretched in anirregular and non-controllable manner. Further, particularly severestresses are created in the edge of the film at the line where the moldcavity joins the mold-half meeting faces. This situation tends to tearthe film or at least to stretch it inelastically whereby a weakness isimparted thereto. Even more disadvantageous is the fact that compositefilm-foam articles prepared in this manner tend to delaminate andliterally fall apart when subjected to stress, particularly to bendingor creasing stress.

It is therefore an object of this invention to provide a film-foamarticle which does not suffer from the disadvantages of the prior art.

It is another object of this invention to provide an improved processfor the production of film-foam composite articles.

It is a further object of this invention to provide an improved processfor the manufacture of shoe inner soles.

Other and additional objects of this invention will become apparent froma consideration of this entire specification including the drawing andclaims appended hereto.

In accord with and fulfilling these objects, this invention resides, inone of its aspects, in a process for the production of film-foamarticles having only a single film layer coating the foam memberthereof. In the process of this invention, a bipartite mold is used asin the prior art. This mold has a cavity containing longitudinalshoulders therein upon which is placed the film coating member such thatthis film drapes between the shoulders and rests upon the bottom of themold cavity.

A batt of non-woven fabric is placed up on the draped film member. Thisbatt may be constructed of substantially any fiber desired such asnylons, polyesters, polyacrylics, modacrylics, cellulosics, wools, etc.It is preferred to utilize relatively long fibers in producing the battsuch as for example about 3 to 6 cm. long, preferably about 4 cm. It isalso preferred to use fairly rough staple fibers such as for exampleabout 15 to 30 denier, preferably about 20 denier. It is essential tothe practice of this invention that the batting used be needled.Needling imparts strength to the batt and makes such resistant todelamination. It has been found that when a non-needled batt ofnon-woven fabric is used, the subsequent foaming process, which will bedescribed below, tends to cause the batt to separate from the coatingfilm whereby is created a composite article having film on one side,non-woven fibrous batt on the other side and foam in between. Needlingtends to increase the rigidity of the batt as well as the bulk densitythereof whereby it remains properly positioned adjacent to the coatingfilm.

A foam-forming composition is placed on the nonwoven batt and the moldhalves closed taking care to insure that neither the film nor thebatting edges are disposed between the meeting surfaces of the moldhalves. The foam forming material is then permitted to foam whereby itimpregnates the non-woven fabric by reason of the pressure exerted bythe foam filling the mold cavity. The expanding foam forces the filmcoating member to fill out the mold cavity by slipping off theaforementioned shoulders and being pressed into the cavity recesses.

In another aspect of this invention vacuum may be applied to therecesses of the mold cavity in order to aid in filling out the cavity bythe foam and insuring that the film coating member conforms to allshapes of the mold cavity. This vacuum may be drawn throughappropriately positioned and sized channels through the mold body as isknown in the vacuum forming art. It is preferred to position at leastsome of the vacuum channels in the deepest and most remote recesses ofthe mold in order to insure filling of the most inaccessible areas.

As is known in the prior art, the expanding foam is self-adherent bothto the non-woven fibrous batt and to the film coating member under theconditions of foaming. Thus there is created a flexible article havingexcellent dimensional stability, strength and good continued integrity.

The coating film used in this invention may be of any of the known filmforming resilient materials such as for example polyvinyl chloride,polyvinylidene chloride, polyethylene, expanded polystyrene,ethylenevinylacetate copolymer, polypropylene, acrylate homo andcopolymers etc. It is preferred to use polyvinylchloride or expandedpolyvinylchloride film in this use.

The foam material used in this invention may be any of those known inthe art such as polyurethane, flexible polyvinylchloride, flexiblestyrene-acrylo-nitrile-butadiene, polyisoprene, polychloroprene, etc.which can be manufactured by known processes using internally producedblowing agents or externally added artificial blowing agents. The natureof the foam is to a great extent determined by the particular end use towhich the composite product will be put. It is preferred for mostgeneral applications to use an arylene di-isocyanate-polyester derivedpolyurethane flexible foam.

It should be kept in mind that all of the constituents of the instantdescribed composite article must be compatible such that the presence ofany of the constituents will not be detrimentally aifected b theprocessing conditions required by reason of the presence of the otherconditions. Thus, for example, it would not be par ticularly effectiveto use a coating film having a melting point below the foamingtemperature of the foamforming material utilized.

It is still another aspect of this invention to produce a still moreuseful composite article, particularly well suited to use in the shoeindustry. Thus it is possible to provide the shoe outer sole at the topof the mold such that the foam will adhere thereto upon filling of themold cavity. In this manner the composite inner-outer sole can beproduced in a single operation if desired. Positioning of the outer solecan be accomplished by insertion thereof between the meeting faces ofthe half molds and use this member to form the mold seal gasket.

This invention will be better understood with reference to the drawingin which FIGS. 1 through are all front elevations in section of theprocess of this invention showing the sequential process steps.

Referring now to this drawing, FIG. 1 shows the lower half 1 of abipartite mold having a cavity 2 and meeting faces 3 and 3. This mold isso constructed that shoulders 4 and 4 are provided about the peripheryof the cavity 2 thereof. These shoulders preferably have sloping upperfaces 5 and 5'. An appropriately shaped film 6 is draped between theshoulders 4 and 4 and the bottom 7 of the mold.

FIG. 2 shows the second step in the process wherein a non-woven textilefabric 8, of the type described above, is disposed upon the film.

FIG. 3 shows the third step in the process wherein a foam-formingmaterial is disposed upon the non-woven textile fabric 8. and the tophalf 10 of the bipartite mold is closed so that its meeting faces 11 and11 close upon the meeting faces 3 and 3 of the bottom half 1 of thebipartite mold. Car must be taken to insure that neither the film 6 northe non-woven fabric 8 are trapped between the meeting faces 3, 3', 11and 11' of the mold halves 1 and 10. In FIG. 4 there is indicated thatthe foam-forming material is starting to expand into a foam 12 forcingexpansion of the coating film 6 to fill the mold cavity 2. Filling ofthe mold cavity by the foam fabric-film composite is aided by thepresence of channels 13 through which a vacuum is drawn whereby insuringthat the film and its associated components reach all areas of the mold.

In FIG. 5 there is shown a completed composite article 14 in accord withthis invention having a coating film 6,. non-woven textile fabric 8,impregnated and coated with foam 12 which composite completely fills themold cavity as set forth above.

After the foaming has been completed and the mold cavity substantiallyor completely filled with the foamed composite article, it has beenfound desirable to permit the article to remain in the mold for a shorttime to permit the foam to set and stabilize itself. It is preferred topermit up to about 15 minutes residence time for stabilization andsetting of the foam whereupon the composite article can be removed fromthe mold and used.

It has been discovered that it is preferred to practice the process ofthis invention in such manner that the mold is substantially gas tight.In the prior art, no particular emphasis has been placed upon the gastightness of the mold since it is known that a foaming process generallyworks substantially equally as well in a gas tight or open mold cavity.In accord with the practice of the invention wherein suction is appliedthrough the channels referred to above, it has been found that theincreasing pressure applied to the top of the foam by reason of residualair being compressed in the space above the foam aids in securing goodmold feature reproducibility since this excess pressure tends to forcethe coating film down tightly against the mold.

An alternate processing technique according to this invention envisionsapplying vacuum through the above referred to channels prior to closingof the mold halves whereby the coating film, and if desired thedeposited non-woven textile fabric, whereby the film conforms to thecontours of the bottom mold prior to foaming of the foam-formingmaterial. Either alternative has been found to be satisfactory.

It is within the spirit and scope of this invention to provide that thecoating film conforms to the contours of the mold by a cold drawingprocess since it hasbeen found that where this film is heated to toohigh a degree and then suitably formed, it looses its elasticity inaddition to becoming weakened due to stretching and the thinning thataccompanies such stretching.

EXAMPLE The bottom half of a mold has a cavity which corresponds to thecontour of a sole. The length of the cavity amounts to 23.5 cm., thedepth up to 2 cm. A slanted shoulder, measuring 1 cm., runs along theside wall of the cavity. A polyvinylchloride film which is commerciallyavailable under the name Hella, is placed into this hollow mold. Thecontours of this film correspond approximately to the side walls of thecavity in the bottom half-mold. However, the film is cut in such a waythat it protrudes approximately 1 cm. beyond the outside of the cavity.It thus covers the shoulders entirely. A needled non-woven fabric madeof nylon fibers, is placed upon this film. After needling, the weight ofthe fabric material is, for instance, 100 g./m. The individual fiberlength exceeds 4 cm., and the fiber is 20 den.

A piece, whose contours correspond exactly the measurements of theindentations in the bottom mold-half is cut out of the needled non-wovenfabric material and is inserted. The shoulder is not covered by thefabric only covering film lies there. Subsequently, 50 g. of a paste ispoured on it. The paste is prepared by mixing together 60 parts of apolyester prepolymer produced by the reaction of adipic acid and 1,6hexanediol, and 40 parts of tolylenediisocyanate.

Then, the upper mold-half is closed taking care not to jam in the filmbetween the upper and lower mold-halves along the contact points. Themold is closed so tightly that it may resist a pressure of approximately5 atm. The paste now starts to foam in the mold, and the foam is evenlydistributed within the needled fabric. Thus, the foam also adheres tothe fiber structure of the needled fabric. At the same time, thecustomary fervent adhesion between the foam and the covering film takesplace.

After approximately 5 to minutes, the mold can be opened. The finished,fiber-reinforced insole, which is partially covered with a protectivefoil, is still warm to the touch, after removal from the mold. After acooling off period, the same can be rolled or exposed to other heavyduties (stresses), without the danger of breaking which has persisted upto now. At the same time, the edges of the sole are exact and distinct.

What is claimed is:

1. A method of forming a composite foam containing article whichcomprises providing a mold having a cavity in the shape of the desiredarticle, which cavity has freely accessible shoulders protruding fromthe side wall thereof; positioning a film in said cavity with the endsthereof resting on said shoulders said film is at least one memberselected from the group consisting of polyvinyl chloride, polyvinylidenechloride, polyethylene, expanded polystyrene, ethylenevinylacetatecopolymer, polypropylene and acrylate homoand copolymers and theremainder draped between said shoulders; providing a needled, non-woventextile fabric on said draped film; providing a foamable polyurethanecomposition on said fabric and said cavity; closing said mold such thatsaid film ends are free of said closure; and causing said polyurethaneto foam whereby said foam impregnates said fabric, adheres to the fibersof said fabric and adheres to said film, and whereby said foam fills outsaid cavity and forces said film into the peripheral shape of saidcavity.

2. Process as claimed in claim 1 wherein said mold is gas tight whenclosed.

3. Process as claimed in claim 1 wherein said mold has provided in therecesses thereof channels and wherein suction is drawn through saidchannels.

References Cited UNITED STATES PATENTS 2,728,702 12/1955 Simon et al.264- 2,879,197 3/1959 Muskat et al. 264-45 2,976,577 3/1961 Gould 264-453,258,511 6/1966 MCGregor 264-45 3,215,764 11/1965 Haworth 264-244JULIUS FROME, Primary Examiner L. GARRETT, Assistant Examiner US. Cl.X.R. 264-54

